1. Field of the Invention
The present invention relates to a method and system for spinal fixation, stabilization and/or fusion of the human occipito-cervical junction. Additionally, the invention is further directed to a method and apparatus for the treatment or mitigation of neurological conditions underlying neurobehavioral disorders arising as a result of skull base, craniocervical and posterior fossa abnormalities, which, in a subset of individuals, occur in conjunction with or underlie neuro-behavioral disorders such as autism and the autism spectrum of disorders, bipolar disorder and other neurological disorders, through the recognition, diagnosis, normalization of craniospinal relationship, fixation, stabilization and/or fusion of the human occipito-cervical junction.
2. Description of the Related Technology
The normal range of motion of the craniospinal junction includes 27° of flexion and extension, and 90° of lateral rotation; the craniospinal junction is thus the most mobile and articulatable part of the human body. It is also the most active part of the human body in movement throughout the day, typically performing greater than 3 million motions a year. The craniospinal junction transmits the entire nervous structure to the body (with the exception of the vagus nerve), and is thus unfortunately susceptible to a host of degenerative disorders. Emblematic of these is rheumatoid arthritis, a chronic degenerative condition that arises in 2% of the population, causing predictable changes in the joints and bone structure of the cervical spine, often including vertical migration of the odontoid and trauma to the ligamentous structures of the craniocervical junction.
Up to 25% of rheumatoid arthritis sufferers develop atlantoaxial subluxation and 9% develop basilar invagination. Clinically these patients invariably experience severe neck pain and neurological deficits, including weakness and sensory loss. Untreated, patients suffer progressive decline, losing the ability to walk. The untreated patient with myelopathy due to compression of the spinal cord has a 50% likelihood of dying within 1 year. Surgical intervention is therefore necessary to stabilize the craniocervical junction, restore neurologic function and prevent further neurologic deterioration. However, occipitocervical stabilization in rheumatoid arthritis can be especially challenging because of such factors as poor bone quality, poor nutritional status and long term steroid use.
There are also other common causes of cranio-cervical instability, including traumatic fractures, which can include approximately 3,000 fractures of the upper spine related to head trauma each year; congenital diseases, including Down's, Morquio's and spondyloepiphyseal dysplasia syndromes, with a prevalence of at least 50,000; osteogenesis imperfecta, with a prevalence of 7,000 patients; cancer, with about 1000 cases per year; and numerous causes of bone softening. Tumors and infections may also cause destruction of the stabilizing elements.
A large, yet undefined, group of patients suffering from neurological instability due to craniocervical abnormalities lies in a subset of individuals diagnosed with neuropsychiatric disorders, which include autism and the autism spectrum of disorders (eg. Asperger's Syndrome), autism, Attention Deficit Hyperactivity Disorder, schizophrenia, and also other neurological conditions that include some forms of sleep apnea, dyslexia, GERDS, speech dyspraxia, idiopathic scoliosis, to mention a few. These conditions often harbor underlying, usually undiagnosed, disorders of the brainstem and spinal cord which result from mechanical deformation and abnormal mechanical stresses arising in the neuraxis at the craniocervical junction. The neurological and neurosurgical literature is replete with the neurological symptoms and signs that result from well known entities, such as retroflexion of the odontoid, platybasia and the various forms of basilar invagination. However, there has been no recognition of the relationship between mechanical strain forces per se and the development of neurological conditions that underlie many neurobehavioral disorders, as well as other common disorders such as dyslexia and sleep apnea.
The clivioaxial angle is depicted in FIG. 1, while an example of basilar invagination is depicted in the image that is shown in FIG. 2, with compression to the brainstem being clearly visible. These conditions have been reported to cause such symptoms as sleep apnea, delayed speech, gastroesophageal reflux, and altered behavior such as attention deficit disorder, headaches, and a myriad of other sensory-motor syndromes. The ubiquity of craniospinal junction pathology has only recently been appreciated.
Hitherto, patients undergoing craniospinal stabilization have required an arduous surgery and recovery. Some patients undergo a decompressive surgery from the front of the neck (transoral resection of the uppermost part of the spine), followed by fusion in the back of the neck, and followed by 3 months of stabilization in a halo brace, which encompasses the head (held by 4 screws in the skull) and the upper body.
Numerous fixation devices have been described such as those that are disclosed in U.S. Pat. Nos. 5,030,220; 5,034,011; 5,545,164; 5,507,745; 6,547,790; 6,524,315; 6,902,565 B2 and U.S. Published Patent Applications US2005/0288669 A1; US2005/0283153 A1 and US2005/0080417 A1, all of which are hereby incorporated by reference as if set forth fully herein.
A need exists for a system and methodology that accomplishes the goals of recognition of the subtler forms of craniocervical and corresponding medullospinal deformity, measurement of the deformity, reduction of deformity through normalization of the craniospinal relationship, successful immobilization and fusion of the craniospinal junction, in a shortened surgery, thereby allowing the patient to return to a normal quality of life within a shorter period of time.